A web proxy server is a computer situated between your PC and a website server you are requesting a data/webpage from. There are two common reasons for using a web proxy:
- To speed up browsing by caching webpage data (a Web cache or CDN) therefore saving a full trip and download from the website you are visiting.
- To stay anonymous towards the website you are visiting whereby the web proxy acts as a “go between”. The website server will only see and/or log the proxy IP address, not your machines IP address.
The visual diagram 1.a below shows how and where a proxy is located on the network chain with further explanation below (click to enlarge the diagram).
- Computer number #1 is your home machine, its IP address is 127.158.84.110. Lets say you open your web browser and enter the website address www.example.com and hit enter. Your computer will send a ask for www.example.com but because you are using a proxy server, that request will be sent to the proxy server first, not the www.example.com web server (yet).
- Computer number #2 is the proxy server, it’s IP address is 184.108.40.206. The proxy server receives the request from your home computer for www.example.com. It then sends the same request to the www.example.com web server, but uses its own IP address of 220.127.116.11, not your home computers IP address.
- Computer number #3 is the web server for www.example.com. It receives the request from the proxy server, and logs its IP address of 18.104.22.168. It then sends the web page back to the proxy server, that then sends it back to your home computer, completing the entire transfer request.
- Number #4 in our diagram is the proxy servers cache. When the Proxy receives the webpage from www.example.com it stores a local copy of it (html, images etc) on it’s hard drive along with a time-stamp. Lets say 30 minutes later you decide to visit www.example.com again and your request is sent to the proxy server, but this time the proxy simply checks if the page on the web server has been altered in the past 30 minutes by comparing the time-stamp it recorded, with the last modified date and time of the web page. If the web page has not changed in the past 30 minutes, the proxy server will send the cached local copy of www.example.com web page making the entire process much faster than downloading the page and data again.
The caching example above is one of many ways a proxy decides when to send the cached copy of a web page, and when to retrieve a fresh version, it really depends on the software used and it’s settings.